JP2005352256A - Optical component for single fiber bi-directional transmitting/receiving module and single fiber bi-directional transmitting/receiving module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single fiber bi-directional transmitting/receiving module which has a high degree of freedom in both of transmission and reception and has high optical coupling efficiency. <P>SOLUTION: In the single fiber bi-directional transmitting/receiving module, a flat surface of a semi-spherical lens 10 and a longitudinal side surface of a rectangular prism are stuck together, a filter is disposed on the stuck surface, an optical signal of prescribed wavelength band made incident from the hemispherical surface of the hemispherical lens is reflected on the filter and is emitted from the hemispherical surface and an optical signal of another wavelength band made incident from the hemispherical surface is transmitted by the filter and is emitted from one surface of the side of the width side of the rectangular prism. The single fiber bi-directional transmitting/receiving module comprises an optical component, an optical fiber, a light emitting element and a light receiving element. Therein, the optical fiber, the light emitting element and the light receiving element are arranged around the optical component for single fiber bi-directional transmitting/receiving module such that respective optical axes intersect the filter at approximately 45° for the filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a single-fiber bidirectional transmission / reception module used in a transmission / reception unit of a bidirectional optical communication system that uses optical signals having different wavelengths for transmission and reception in a single optical fiber, and in particular, freedom of optical design for both transmission and reception. The present invention relates to an optical component for a single-fiber bidirectional optical transceiver module having high optical coupling efficiency and a high-performance single-core bidirectional transceiver module using the same.

  A conventional single-core bidirectional transmission / reception module is a light-receiving element that guides an optical signal from a transmitting laser diode (hereinafter referred to as LD), which is a light-emitting element, to an optical fiber and also transmits an optical signal transmitted through the optical fiber. In order to guide to a photodiode (hereinafter referred to as PD), a wavelength filter is disposed between the optical fiber and the LD and PD, and the optical signal path is divided according to the difference in wavelength (for example, , See Patent Document 1).

  1A and 1B are schematic views illustrating the configuration of a conventional single-core bidirectional transmission / reception module, in which reference numeral 1 is an optical fiber, 2 is an LD, 3 is a PD, 4 is a filter, 7 is a ball lens. In FIG. 1A, an example using a filter 4 formed on a glass plate 8 is used, and FIG. 1B is an example using an optical component 9 in which a right-angle prism is bonded through the filter 4. Is shown.

  In the conventional single-core bidirectional transmission / reception module shown in FIG. 1, the signal light from the LD 2 passes through the filter 4 and is coupled to the optical fiber 1, while the signal light from the optical fiber 1 is reflected by the filter 4 and is transmitted to the PD 3 Led to. However, since the signal light from the optical fiber 1 and the signal light from the LD 2 have a large spread as they are, one or more lenses (ball lenses) in addition to the filter 4 as shown in FIGS. The light is generally collected by adding 5, 6, 7).

As another conventional technique, a single-core bidirectional transmission / reception module using an optical component in which a filter is formed on a flat surface of a hemispherical lens has been proposed (for example, see Patent Document 2).
FIG. 2 is a diagram showing another example of a conventional single-core bidirectional transmission / reception module. This module forms a filter 4 on a flat surface of a hemispherical lens 10, and signal light from the LD 2 is transmitted from the hemispherical surface to the hemispherical lens 10. , Is reflected by the flat filter 4, is emitted from the hemisphere again, and travels toward the optical fiber 1. On the other hand, the signal light from the optical fiber 1 is incident from the hemispherical surface, passes through the filter 4 and travels toward the PD 3. At this time, since the filter 4 is inclined with respect to the optical axis, the optical axis is bent and emitted. Therefore, PD3 is arrange | positioned according to this curved axis | shaft.
Japanese Patent No. 2757350 US Pat. No. 5,416,624

However, the above-described prior art has the following problems.
In the prior art described in Patent Document 1, it is necessary to insert a filter and a lens between the LD or PD and the optical fiber. For this reason, measures such as arranging a plurality of lenses or increasing the focal length are provided in order to secure a space for inserting a lens between the lens and the optical fiber as compared with the case where the optical fiber is simply coupled with the LD and PD. There is a problem that increases the number of parts and complicates assembly work. In addition, since the degree of freedom in optical design is lowered, there is a problem that a design with the highest coupling efficiency cannot always be realized.

  The prior art described in Patent Document 2 integrates a filter and a lens, and with respect to optical coupling between an LD and an optical fiber, an effect equivalent to that obtained by using a ball lens can be obtained, and the degree of freedom in optical design is relatively high. Is also expensive. However, it is necessary to bring the LD and the optical fiber close to each other. Regarding the coupling between the optical fiber and the PD, the condensing effect of the lens is difficult to obtain and the higher the refractive index of the lens, the more light is refracted on the flat surface of the filter Therefore, in order to secure an optical signal to the PD, the degree of freedom in designing the lens angle and refractive index, and the arrangement of the LD and PD are reduced. In general, when the transmission speed is low, the light receiving area of the PD is large and the influence is small. However, since the PD corresponding to a high transmission speed has a small light receiving area, it is difficult to obtain sufficient coupling. In addition, it is extremely difficult to arrange the LD on the transmission side in terms of ensuring optical coupling efficiency. Furthermore, it is difficult to hold the hemispherical lens at a certain angle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a single-fiber bidirectional transmission / reception module having a high degree of freedom in optical design for both transmission and reception and high optical coupling efficiency.

In order to achieve the above object, the present invention is such that a flat surface of a hemispherical lens and a long side surface of a right-angle prism are bonded together, and a filter is provided on the bonded surface, which is incident from the hemispherical surface of the hemispherical lens. An optical signal in a specific wavelength band is reflected by the filter and emitted from the hemisphere, and an optical signal in another wavelength band incident from the hemisphere is transmitted through the filter and emitted from one surface on the short side of the right-angle prism. An optical component for a single-fiber bidirectional optical transceiver module is provided.
The present invention also includes the above-described optical component for a single-fiber bidirectional optical transceiver module according to the present invention, an optical fiber, a light emitting element, and a light receiving element, and the optical fiber, the light emitting element, and the light receiving element. Are arranged around the optical component for the single-fiber bidirectional optical transceiver module so that the respective optical axes intersect at about 45 degrees with respect to the filter. .
In the single-core bidirectional optical transceiver module according to the present invention, the light emitting element is disposed on a side where the emitted light is reflected by the filter and the reflected light is incident on the optical fiber, and the light receiving element includes the filter. It is preferable that the optical signal from the transmitted optical fiber is arranged on the side where the optical signal can be incident.
In the single-core bidirectional optical transceiver module according to the present invention, it is preferable that a transmission light cut filter for removing light from the light emitting element is provided on one surface of the short side of the right-angle prism.
In the single-core bidirectional optical transceiver module according to the present invention, it is preferable that a lens is attached to one surface of the short side of the right-angle prism.

The optical component for a single-fiber bidirectional optical transceiver module and the single-fiber bidirectional optical transceiver module of the present invention have fewer filters and lenses and a lens holding member than those in which a plurality of lenses and filters are disposed. Highly flexible optical system design in space.
Further, an optical module having a high coupling efficiency can be obtained by acting as a ball lens for at least an optical signal having a wavelength reflected by the filter. Further, for the light passing through the filter, the coupling efficiency can be increased by adding a lens.
When transmission is performed on the side reflected by the filter, the influence of noise can be removed by adding a filter that cuts the transmission wavelength to the side of the light receiving element of the right-angle prism. In addition, there is no increase in dimensional constraints due to the addition of a filter.
Since the right-angle prism serves as an optical system and its holding member, the mounting structure on the module is simplified. In addition, since a general-purpose prism can be used, material costs can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 3 is a block diagram showing the first embodiment of the present invention. In this figure, reference numeral 1 is an optical fiber, 2 is a light emitting element LD, 3 is a light receiving element PD, 4 is a filter, 10 is a hemispherical lens, and 11A is an optical component for a single fiber bidirectional optical transceiver module (hereinafter referred to as an optical component). , 12 is a right-angle prism, 12A is a surface on the long side of the right-angle prism 12, and 12B and 12C are surfaces on the short side of the right-angle prism.

  In the present embodiment, in the optical component 11A, the flat surface of the hemispherical lens 10 and the long side surface 12A of the right-angle prism 12 are bonded together, and the filter 4 is provided on the bonded surface, which is incident from the hemispherical surface of the hemispherical lens 10. The optical signal in the specific wavelength band is reflected by the filter 4 and emitted from the hemispherical surface, and the optical signal in another wavelength band incident from the hemispherical surface is transmitted through the filter 4 from the one surface 12C on the short side of the right-angle prism 12. It is comprised so that it may radiate | emit. The other surface 12B on the short side of the right-angle prism 12 can be used as a fixing surface for fixing the optical component 11A to an appropriate inner surface of the exterior body or a substrate.

  The right-angle prism 12 and the hemispherical lens 10 constituting the optical component 11A can be manufactured using various optical transparent materials having the same refractive index. For example, a glass prism or lens such as BK7 is preferable. Further, the dimensions of the right-angle prism 12 and the hemispherical lens 10 are not particularly limited. For example, the right-angle prism 12 can have all short sides of about 4 mm and the hemispherical lens has a radius of about 2 mm. The long side surface 12A of the right-angle prism 12 and the flat surface of the hemispherical lens 10 are bonded using an optical adhesive.

  The filter 4 is a wavelength filter that reflects an optical signal in a specific wavelength band and transmits an optical signal in another wavelength band, and a dielectric multilayer filter or the like can be used. The filter 4 is provided on one of the flat surface of the hemispherical lens 10 and the long-side surface 12A of the right-angle prism 12, and the flat surface of the hemispherical lens 10 and the long-side surface 12A of the right-angle prism 12 are provided. Are placed on the bonding surface. The wavelength selection characteristic of the filter 4 is determined according to the wavelength band of the transmission / reception optical signal to be used. For example, light having a wavelength of about 1310 nm is reflected with respect to light incident at 45 degrees on the filter 4. In addition, it can have a filter characteristic that transmits light in the vicinity of 1550 nm.

  As shown in FIG. 3, the single-fiber bidirectional optical transceiver module using the optical component 11A includes the optical component 11A, the optical fiber 1, the light emitting element LD2, and the light receiving element PD3. The optical fiber 1, the LD 2, and the light receiving element PD are arranged around the optical component 11 A so that their optical axes intersect with the filter 4 at approximately 45 degrees. As shown in FIG. 3, when the other surface 12B on the short side of the right-angle prism 12 is fixed to a horizontal plane, the filter 4 is arranged in a state inclined at 45 degrees with respect to the horizontal plane. The optical axes of the optical fiber 1 and the PD 3 are arranged substantially in a straight line, and these optical axes are perpendicular to the surface 12C on the short side of the right-angle prism 12. The LD 2 is disposed immediately below the optical component 11 </ b> A, and its optical axis is perpendicular to the other surface 12 </ b> B on the short side of the right-angle prism 12.

  With such an arrangement, the optical signal (transmitted light) from the LD 2 is incident on the hemispherical lens 10 from the hemispherical surface, reflected by the filter 4, bent at a right angle, and emitted from the hemispherical surface to the optical fiber 1. Head. On the other hand, an optical signal (received light) from the optical fiber 1 enters the hemispherical lens 10 from the hemispherical surface, passes through the filter 4, exits from the one side 12C on the short side of the right-angle prism 12, and travels toward the PD3.

  As described above, the optical component 11 </ b> A configured by the hemispherical lens 10, the filter 4, and the right-angle prism 12 acts as a ball lens for light having a wavelength reflected by the filter 4, and light having a wavelength that passes through the filter 4. In contrast, since the hemispherical lens 10 and the right-angle prism 12 have the same refractive index, they act as plano-convex lenses. The thickness of the plano-convex lens can be adjusted at a position where the hemispherical lens 10 is attached to the right-angle prism 12.

According to the present embodiment, since the filter 4, the lens, and the lens holding member are integrated, it is possible to design an optical system with a high degree of freedom in a smaller space than in the case where a plurality of lenses and filters are arranged.
Further, an optical module having a high coupling efficiency can be obtained by acting as a ball lens for at least an optical signal having a wavelength reflected by the filter 4.
Since the right-angle prism 12 serves as an optical system and its holding member, the mounting structure on the module is simplified. In addition, since a general-purpose prism can be used, material costs can be reduced.

  FIG. 4 is a block diagram showing a second embodiment of the present invention. The optical component 11B according to the present embodiment has substantially the same configuration as the optical component 11A according to the first embodiment described above, and transmits light to one surface 12C on the short side of the right-angle prism 12 facing the PD 3. A cut filter 13 is provided. The transmission light cut filter 13 is formed of a dielectric multilayer filter or the like, reflects light having the wavelength of the transmission optical signal emitted from the LD 2, and transmits light having the wavelength of the reception optical signal from the optical fiber 1 toward the PD 3. It has wavelength filter characteristics. If necessary, the optical signal incident from the optical fiber may have a characteristic of reflecting light having an unnecessary wavelength.

  Depending on the filter performance of the optical component 11B, a very small part of the optical signal from the LD 2 is transmitted without being reflected by the filter 4 on the flat surface of the hemispherical lens 10, and is repeatedly reflected toward the PD 3 to cause noise. As shown in FIG. 4, by forming a filter 13 that reflects the wavelength of the optical signal from the LD 2 on the one surface 12C on the short side of the right-angle prism 12, the influence of noise can be eliminated. it can. Moreover, the influence of noise can be eliminated by providing a characteristic that reflects a wavelength other than the optical signal that is intended to be received by this module, among optical signals incident from the optical fiber.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained, and the filter 13 that reflects the wavelength of the optical signal from the LD 2 is formed on the surface 12C on the short side of the right-angle prism 12. Thus, the influence of noise can be removed. Further, there is no increase in dimensional constraints due to the addition of the filter 13.

  FIG. 5 is a block diagram showing a third embodiment of the present invention. In the present embodiment, an optical component 11A (or 11B) is disposed in the exterior body 16, and a single-fiber bidirectional optical transceiver module 14A in which the optical fiber 1, LD2, and PD3 are disposed at predetermined positions through the exterior body 16 is illustrated. In this single-core bidirectional optical transceiver module 14A, the optical component 11A has the other surface 12B on the short side of the right-angle prism 12 bonded and fixed to the ceiling inner surface (or inner surface of the lid) of the exterior body 16. The optical fiber 1 has a ferrule 15 at the tip, and is attached to the side wall with the tip of the ferrule 15 inserted into the exterior body 16. The ferrule 15 and PD3 attached to the side wall of the exterior body 16 and the exterior body 16 are arranged so that their optical axes intersect with the filter 4 of the optical component 11A at approximately 45 degrees.

  According to the third embodiment, the same effects as those of the first embodiment can be obtained. Further, the other surface 12B on the short side of the right-angle prism 12 is used as a fixing surface, and this surface is used as the exterior body 16. By adhering and fixing to the inner surface, the filter 4 can be accurately set to 45 degrees with respect to the inner surface of the rectangular exterior body 16, and the other surface 12B on the short side of the right-angle prism 12 is connected to the bottom surface. Since the angle can be accurately set to 90 degrees, the case design becomes easy.

  FIG. 6 is a block diagram showing a fourth embodiment of the present invention. The single-fiber bidirectional optical transceiver module 14B of the present embodiment is configured to include substantially the same components as the single-fiber bidirectional optical transceiver module 14A of the third embodiment. The difference is that LD bare chip 17 and PD bare chip 18 are used instead of LD2 and PD3, respectively.

  According to the fourth embodiment, the same effects as those of the third embodiment can be obtained. Further, by using bare chips for the LD and the PD, the number of mounted LD and PD elements can be increased without increasing the space. Therefore, a small and high performance module can be manufactured.

FIG. 7 is a block diagram showing a fifth embodiment of the present invention. The optical component 19 of the present embodiment has the same configuration requirements as the optical component 11A of the first embodiment shown in FIG. 3, and a plano-convex lens 20 is pasted on one surface 12C of the short side of the right-angle prism 12. It is configured. The added plano-convex lens 20 has a radius of curvature of about 2 mm as in the hemispherical lens 10 and is polished to a thickness of about 0.51 mm to form a ball lens having a diameter of 4 mm together with the lens and prism. Thereby, the coupling efficiency with respect to the transmitted light of the filter 4 can be increased.
Actually, it is not always necessary to form a ball lens, and an optimal optical system is designed by adjusting the radius of curvature, thickness, and refractive index (material) according to whether the LD2 or PD3 is arranged on the transmission side. To do.

  The single-fiber bidirectional optical transceiver module according to the fifth embodiment includes the optical component 11, the optical fiber 1, the light emitting element LD2, and the light receiving element PD3, and the optical fibers 1 and LD2. And the light receiving element PD are arranged around the optical component 11A so that their optical axes intersect the filter 4 at approximately 45 degrees.

  In the fifth embodiment, substantially the same effect as that of the first embodiment can be obtained, and the plano-convex lens 20 is attached to the one surface 12C on the short side of the right-angle prism 12, so that the transmitted light of the filter 4 is transmitted. It is possible to increase the coupling efficiency for.

Each embodiment mentioned above is only illustration of the present invention, and the present invention is not limited to these embodiments, and various changes are possible.
For example, in each of the embodiments, in order to increase the coupling efficiency between the LD and the optical fiber, the LD is disposed on the opposite side of the filter, that is, the side on which the optical component acts as a ball lens. Even if the LD is arranged, it is possible to take optical coupling.
In some cases, an optical resin having refractive index matching may be filled between the light emitting / receiving element and the flat surface of the prism.

It is a block diagram which shows an example of the conventional single fiber bidirectional optical transmission / reception module. It is a block diagram which shows another example of the conventional single fiber bidirectional optical transmission / reception module. It is a block diagram which shows the single core bidirectional | two-way optical transmission / reception module of 1st Embodiment of this invention. It is a block diagram which shows the single core bidirectional | two-way optical transmission / reception module of 2nd Embodiment of this invention. It is a block diagram which shows the single core bidirectional | two-way optical transmission / reception module of 3rd Embodiment of this invention. It is a block diagram which shows the single core bidirectional | two-way optical transmission / reception module of 4th Embodiment of this invention. It is a block diagram which shows the single core bidirectional | two-way optical transmission / reception module of 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical fiber, 2 ... LD (light emitting element), 3 ... PD (light receiving element), 4 ... Filter, 10 ... Hemispherical lens, 11A, 11B, 19 ... Optical component (Optical component for single fiber bidirectional optical transmission / reception modules). DESCRIPTION OF SYMBOLS 12 ... Right angle prism, 13 ... Transmission light cut filter, 14A, 14B ... Single fiber bidirectional optical transmission / reception module, 17 ... LD bare chip, 18 ... PD bare chip, 20 ... Plano-convex lens

Claims (5)

  The flat surface of the hemispherical lens and the surface on the long side of the right-angle prism are bonded together, and a filter is provided on the bonded surface, and an optical signal in a specific wavelength band incident from the hemispherical surface of the hemispherical lens is reflected by the filter. The optical signal for a single-fiber bidirectional optical transceiver module is characterized in that an optical signal of another wavelength band emitted from the hemispherical surface and transmitted from the hemispherical surface is transmitted through the filter and emitted from one surface on the short side of the right-angle prism. parts.   An optical component for a single-fiber bidirectional optical transceiver module according to claim 1, an optical fiber, a light emitting element, and a light receiving element, wherein the optical fiber, the light emitting element, and the light receiving element are respectively A single-fiber bidirectional optical transceiver module, wherein the optical fiber is disposed around the optical component for the single-fiber bidirectional optical transceiver module so that an optical axis intersects with the filter at approximately 45 degrees.   The light emitting element is disposed on a side where the emitted light is reflected by the filter and the reflected light is incident on the optical fiber, and the light receiving element receives an optical signal from the optical fiber that has passed through the filter. The single-fiber bidirectional optical transceiver module according to claim 2, wherein the single-fiber bidirectional optical transceiver module is disposed on a possible side.   The single-fiber bidirectional optical transceiver module according to claim 3, wherein a transmission light cut filter for removing light from the light emitting element is provided on one surface of the short side of the right-angle prism. The single-fiber bidirectional optical transceiver module according to any one of claims 2 to 4, wherein a lens is attached to one surface of the short side of the right-angle prism.

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